The microelectronic, such as semiconductor and optoelectronic, industries have seen the requirement for smaller and smaller device geometries over the past several years. While in some areas of device fabrication sub-micron device geometries have been common place for a number of years, in other areas, such as liquid crystal displays (LCDs), organic light emitting diodes (OLEDs) and a variety of radio frequency (RD and microwave devices (e.g. RFICs/MMICs, switches, couplers, phase shifters, SAW filters and SAW duplexers), such device geometries are only recently approaching the 1 to 5 micron level. As a result, for these latter areas, imaging layers sensitive to deep UV radiation (e.g., 248 nm) are desirable.
As a result, new photopolymers based on poly(hydroxystyrene) (PHS) and chemical amplification strategies were developed to initially meet that desire. (Introduction to Microlithography by L. F. Thompson, C. G. Willson and M. J. Bowden, 1994, p. 212-232 and H. Ito, IBM J. Res. Dev., 2001, 45(5) 683). While PHS is relatively transparent to 248 nm light, as compared to novolak, it has been reported that “PHS and its derivatives . . . have unfavorable dissolution and inhibition properties compared to novolaks.” (Dammel, et al. Proceedings of SPIE—The International Society for Optical Engineering (1994), 2195 (Advances in Resist Technology and Processing XI), 542-58). In this regard, adding dissolution rate inhibitors such as diazonaphthoquinone (DNQ), which approach had been successful with novolaks, for positive tone systems, was problematic for PHS. Thus, the aforementioned chemical amplification approach was developed. However, PHS photoresists are known to have limited thermal stability and limited resistance to common dry etch processing. Imageable polymers that consist of norbornene-type repeating units are known for their excellent thermal stability, low dielectric constant and etch resistance. Therefore, it is believed that it would be advantageous to provide polymers that would be useful for forming photoresist compositions that are sensitive to actinic radiation and that exhibit enhanced thermal stability and etch resistance as compared to currently known PHS systems. Thus, polymers encompassing repeating units derived from norbornene-type monomers and appropriate non-norbornene-type monomers, polymer compositions thereof and the use of such compositions are described hereinafter.